Method for treating exhaust gas and an apparatus therefor

ABSTRACT

A powdery adsorbent is mixed with an exhaust gas containing fine particles and a noxious and malodorous gas component in gas pipelines, adhering the fine particles to the powdery adsorbent and adsorbing the noxious and malodorous gas with the powdery adsorbent. The powdery adsorbent is then fed to dust collectors where the exhaust gas is separated from the powdery adsorbent and is purified. The separated powdery adsorbent comes in contact with a hot blast at a high temperature, or else is indirectly heated in a pipeline and the adsorbed gas is thereby desorbed. Further, a part of or all of the desorbed powdery adsorbent comes in contact with a hot blast at a higher temperature than the above mentioned temperature, or is indirectly heated in a pipeline, and thereby the fine particles adhered to the powdery adsorbent are thermally decomposed. In this way, the powdery adsorbent is regenerated, and can be returned to be mixed with the exhaust gas in order to be reused.

BACKGROUND OF THE INVENTION

(1) Technical Field

The present invention relates to a method for treating an exhaust gasand an apparatus therefor which can efficiently carry out a treatment ofseparating a noxious and malodorous gas and concentrating the gas to asmall flux. The method is for treating low concentration exhaust gasescontaining fine particles and a noxious and malodorous gas component,such as exhaust gases from car coating. In low concentration exhaustgases containing fine particles and a noxious and malodorous gas, thefine particles, for example plasticizers, higher fatty acids, lampblack,pitch, etc., may deteriorate an adsorbent. Such exhaust gas is alsoproduced in printing, steel pipe production presses, etc.

The meaning of "fine particles" as mentioned in the specificationincludes, generally, adhesive dust, mist and particulate high boilingpoint substances. "Mist" means liquid fine particles, and the "highboiling point substances" mean a high boiling point gas and a highboiling point mist.

(2) Background Art

A so-called deodorizer for separating a noxious and malodorous gas froman exhaust gas containing a low concentration noxious and malodorous gassuch as organic solvents, etc., is widely used in manufacturingprocesses in various industries. A typical prior art example of adeodorizing treatment of this type appears in FIG. 1 as an apparatus fortreating an exhaust gas from a car coating process.

A coating booth 201 in a line for coating car chassis generates anexhaust gas containing adhesive dust consisting of very fine paintresidue with a not more than 10 μm particle diameter and a noxious andmalodorous gas component such as organic solvents. This exhaust gasneeds to be purified. Therefore, the exhaust gas is dusted by initiallypassing the exhaust gas through a wet static dust collector 202 via anexhaust pipeline 14. At this time, for preventing dust from sticking tothe electrodes, a sprinkling on the dust collector electrodes isperformed. The dusted exhaust gas is fed to a humidity/temperatureregulator 203 to be dehumidified and adjusted in temperature.Thereafter, the noxious and malodorous gas component of the exhaust gasis concentrated and separated in a honeycomb type concentrationapparatus 204. The purified and treated air is again fed to the coatingbooth 201, passing through another humidity/temperature regulator 205via a pipeline 19. The noxious and malodorous gas concentrated by theconcentration apparatus 204, after being separated, is discharged out ofthe room through a heat recovering and exchanging device 207 as anexhaust gas after being neutralized by oxidation treatment in acatalytic oxidation apparatus 206.

As apparatuses for direct treatment of an exhaust gas, there areavailable directly firing furnaces, catalytic oxidization apparatuses,adsorptive recovery systems, chemical solution cleaning systems, etc.These apparatuses become further economically disadvantageous withdecreasing concentrations of contaminants. As treatment systemscombining small devices, with the exhaust gas once concentrated toprovide a small flux, of primary interest now is the above-describedconcentration apparatus 204 making use of a rotor formed in a honeycombshape of an adsorbent such as activated charcoal, etc. This apparatus isadvantageous in its excellent operational economy, but involves thebelow-mentioned problems.

Because the adsorbent is formed into a honeycomb shaped rotor, the costof the apparatus is over ten times as high as the material adsorbent.Moreover, because the adsorbent is formed in an admixture with anorganic binder and auxiliary materials, its reactivation is difficultwhen its adsorptive performance has deteriorated. Furthermore, becauseof its heating system using hot blast for regeneration in order toconcentrate the exhaust gas, indirect heating is not applicable. As aconsequence, the degree of concentration is limited to 10 to 15 times onaccount of the heating calories for the honeycomb rotor, andsimultaneous heating of not only the adsorbent, but other combinedmembers, like the auxiliary materials, etc., is necessary, thusrequiring large heating calories therefor.

Particularly, in the case of the treatment of the exhaust gas from carcoating, because of the adhesive dust being contained in the exhaustgas, this adhesive dust sticks on the surface of the honeycomb shapedrotor, thereby blocking the rotor, and resulting in an extremely loweredadsorptive performance. This necessitates its combination with a wetstatic dust collector 202 with a high performance and high price,raising the problem of a high overall cost of the equipment.

On the other hand, the exhaust gas produced in printing processescontains high boiling point substances, such as plasticizers and woodtar, which could deteriorate the adsorbent forming the honeycomb shapedrotor. This necessitates the use of an expensive floor-fixed typeadsorption tower as pretreatment equipment, which also increases theoverall cost of the equipment.

OBJECTION OF THE INVENTION

It is, accordingly, an object of the present invention to provide amethod and apparatus for exhaust gas treatment which can realize ahighly efficient exhaust gas treatment in a high concentration stateusing a compact structure and at a low running cost, wherein a noxiousand malodorous gas in the exhaust gas is efficiently removed byadsorption.

SUMMARY OF THE INVENTION

The present invention is provided with means to achieve the aboveobject.

The present invention provides a method for treating exhaust gascontaining fine particles having organic compounds as a main componentand a noxious and malodorous gas, which comprises the steps of:

mixing a powdery adsorbent into the exhaust gas to adsorb the noxiousand malodorous gas,

separating the powdery adsorbent from the exhaust gas after the mixingstep,

regenerating the separated powdery adsorbent by heating the powderyadsorbent to desorb the noxious and malodorous gas from the separatedpowdery adsorbent, and

returning the powdery adsorbent regenerated at the regenerating step soas to be utilized in the mixing step.

Also, the invention provides an apparatus for treating an exhaust gascontaining fine particles having organic compounds as a main componentand a noxious and malodorous gas, which comprises:

means for adsorbing the noxious and malodorous gas, the adsorbing meanscomprising (a) a means for mixing a powdery adsorbent into the exhaustgas, and (b) a means for separating the powdery adsorbent from theexhaust gas conveyed from the mixing means,

means for regenerating the powdery adsorbent by heating the powderyadsorbent separated by the separating means to desorb the noxious andmalodorous gas from the separated powdery adsorbent, and

means for conveying for returning the regenerated powdery adsorbent tothe mixing means.

In a preferred embodiment, the powdery adsorbent is implemented by apowder of hydrophobic zeolite.

In another preferred embodiment, the separating means comprises firstand second dust separating devices connected in a series to convey theexhaust gas separated by the first dust separating device to the seconddust separating device and disposed so as to convey a part of thepowdery adsorbent separated by the first and second dust separatingdevices to the mixing means prior to the first dust separating device.The conveying means is disposed to return the powdery adsorbentregenerated by the regenerating means to an inlet side of the seconddust separating device.

In still another preferred embodiment, the separating means comprisesthree or more dust separating devices connected in series to convey theexhaust gas separated by each of the dust separating devices to the nextdust separating device disposed downstream of the former dust separatingdevice and disposed so as to convey the powdery adsorbent separated bythe first dust separating device to the regenerating means and to returnthe powdery adsorbent separated by each of other dust separatingdevices, except the first dust separating device, to an inlet side ofthe former dust separating device disposed just before each of the dustseparating devices. The conveying means is disposed to return thepowdery adsorbent regenerated by the regenerating means into an inletside of the last dust separating device.

In a further preferred embodiment, the regenerating means comprises:

means for heating the powdery adsorbent separated by the separatingmeans at a first temperature by indirectly heating or directly heating amixture of the separated powdery adsorbent with a regeneration gas todesorb the noxious and malodorous gas from the separated powderyadsorbent, and

means for heating a part of all of the powdery adsorbent adsorbed by thefirst high temperature heating means at a second temperature higher thanthe first temperature by indirectly heating or directly heating amixture of the desorbed powdery adsorbent with a gas at the secondtemperature to thermally decompose the fine particles adhering to thedesorbed powdery adsorbent.

In a still further preferred embodiment, the apparatus further comprisesmeans for electrostatically charging the powdery adsorbent conveyed fromthe regenerating means to the mixing means.

In a still further preferred embodiment, the conveying means is a meansfor pneumatically conveying the powdery adsorbent by a cool blastprocess.

In yet a further preferred embodiment, the apparatus further comprisesmeans for neutralizing and deodorizing the noxious and malodorous gasconcentrated by the regenerating means by collection and/or oxidativedegradation of the noxious and malodorous gas.

In a still further preferred embodiment, the neutralizing anddeodorizing means is implemented by an adsorption type collectingdevice.

In a still further preferred embodiment, the neutralizing anddeodorizing means is implemented by an oxidative degradation device.

According to the present invention, by mixing the exhaust gas and apowdery adsorbent with each other in the conveying step using apneumatic conveying means, a highly efficient adsorption of gascomponents and adhesion of fine particles, in a state of direct contactwith each other, are effected. On account of this, the adsorbingtreatment may be performed with a simple construction of pneumaticconveyance pipelines, so that such complex mechanisms such as honeycombtype concentration devices, etc., may be omitted.

From the adsorbent on which the adsorption and adhesion have been made,after being separated from the exhaust gas by a separating means such asa bag filter, cyclone or the like, the noxious and malodorous gas aredesorbed in a small flux of gas for regeneration that is fed in by anindirect heating means such as a rotary kiln and a ribbon mixer or byindirect heating such as bringing into contact with a hot blast. Thisyields a regenerated powdery adsorbent, which is returned to thepneumatic conveying means used in the adsorbing step.

Efficient desorption is permitted to be made with only a small flux ofgas for regeneration being required. The desorbed concentrated gas is ina highly concentrated state, so that it may be neutralized by the use ofsmall scale combustion equipment or small collecting equipment whendisposing of the concentrated gas.

The fine particles adhering to the powdery adsorbent are continuously orperiodically removed by a separately installed heating device. Themalodorous gas generated by the heating device is disposed of by anycombustion apparatus. The ash from the fine particles which haveaccumulated during repetitive heating treatment may be separated byperiodically putting the adsorbent into a water tank and takingadvantage of the sp.gr. difference. The purified adsorbent may be reusedafter drying.

Further, according to the preferred embodiment, when the regeneratingmeans comprises a low temperature heat treating means and a hightemperature heat treating means, the adsorbent laden with adsorptivesand adhesives is separated for the exhaust gas by separating meansincluding a cyclone separator, bag filter, etc. Thereafter, thedesorption and separation of the noxious and malodorous gas and thethermal decomposition of the fine particles are performed by the lowtemperature heat treating means and the high temperature heat treatingmeans, and the adsorbent regenerated by the treatment through the twokinds of heat treating means is mixed into the exhaust gas and is thusreused for exhaust gas treatment.

In regenerating the adsorbent, the temperature conditions forregeneration are different between the treatment of the noxious andmalodorous gas and the treatment of the fine particles. The temperaturerange suitable for the desorption of the noxious and malodorous gas is120° to 250° C., in which range the noxious and malodorous gas can bedesorbed from the adsorbent. On the other hand, in the case of the fineparticle, for example, paint mist, oxidative degradation is required inaddition to thermal decomposition. Decomposition will become noticeablefrom around 250° C. but for complete decomposition, high temperatures of350° to 600° C. will be needed. In the case of high boiling pointsubstances, the conditions vary depending on the natures of thesubstances, but generally, desorption is accomplished at temperatures of250° to 350° C., and part of the substances are thermally decomposed toproduce tar or carbon. Considering the above, temperatures from 350° to600° C. are needed for regeneration.

The expressions "low temperature heating treatment" and "hightemperature heating treatment" are intended to express the relativedifferences between the high and low temperatures occurring in treatmentwhen comparing the above two heating treatments with each other. Both ofthe "low temperature heating treatment" and the "high temperatureheating treatment" are carried out at high temperatures equal to or over120° C.

Low temperature heat treatment is necessary for the following reasons.One reason is that, at the temperatures needed for the treatment of thefine particles, the noxious and malodorous gas could also be desorbed,but could also be ignited, as the temperature is higher than theignition point. Since the gas concentration is very high, its combustionheat would cause the process temperature to rise considerably, whichcould cause trouble in the regeneration processing section due toabnormal rises in the temperature. Another reason is that in recoveringthe noxious and malodorous gas, low temperature treatment causes lessdecomposition, and make it possible to recover the products in a higherpurity and in a liquid state, with a smaller content of impurities suchas high boiling point substances.

For low temperature and high temperature heat treatment, a rotary kiln,ribbon mixer, or the like can be used to deliver the required heat fortreatment. Such equipment can distribute heat uniformly by a pneumaticheating method, preferably by hot blast, and enhances the economy, sincethe high temperature gas generated from the oxidative cracker, such as acatalytic oxidization device or direct firing combustion furnace, at alater step, can be used as the heat source. The flow rate of the hotblast used for low temperature heat treatment is sufficiently small withrespect to the exhaust gas, and since the noxious and malodorous gas inthe exhaust gas is mixed into the hot blast while flowing at a smallflow rate, the noxious and malodorous gas concentration in the mixtureis greatly increased as a result of the difference in flow rates betweenthe exhaust gas and the hot blast.

The adsorbent, after low temperature heat treatment, is heat-treated ata temperature equal to or higher than 350° C. so that the fine particlesare removed by thermal decomposition as well as by oxidativedegradation. The high temperature heat treating device also utilizesexhaust gas from the oxidative cracker, enhancing the economy by hotblast heating, and is desirable for uniform continuous treatment.

In the low temperature and the high temperature heat treating means, theequipment for generating the heating gas to be mixed with the adsorbentcan be constructed from a pneumatic conveyance pipeline. The adsorbentis effectively heat-treated while being carried through the pneumaticconveyance pipeline into the cyclone. Also, the adsorbent isheat-treated at high temperature using a rotary kiln or a ribbon mixer.

When recovering the concentrated gas after low temperature heattreatment, the gas is introduced into a small-size solvent collectingdevice having a flow rate equivalent to that of the gas. In the case ofneutralizing and deodorizing the gas by oxidative degradation, the gasis introduced into the oxidative cracker together with the exhaust gasafter high temperature heat treatment.

The adsorbent, after heat treatment, is cooled and then returned to theadsorption pneumatic conveying means at the first adsorbing step.However, depending on the kinds of substances contained in the exhaustgas, malodorous components generated during the decomposition may remainwith the adsorbent, and such malodorous components may contaminate thepurified gas used as the carrier gas to transport the adsorbent. Oneapproach to the resolution of this problem is to use a cooling devicecomprising a pneumatic conveying means using atmospheric air as thecarrier fluid, a cyclone separator, and a bag filter, thereby providingseparation between the adsorbent and the cooling air. This arrangementhas the advantage that the malodorous components carried with theadsorbent are separated from the cooling air at the same time that theadsorbent is cooled. For this cooling means, a multi-step system isdesirable as the cooling of the adsorbent, and the removal of themalodorous components can be accomplished in a more efficient mannerwhen the same amount of cooling air is used.

In case the fine particles and the noxious and malodorous gas areremoved simultaneously, it is to be well remembered that the removingmechanisms are different for the individual substances.

Adhesive dust from, e.g., painting can be removed by a sticking actionwith relative ease, as its particles collide and/or contact with theadsorbent when the particle size is not less than 10 μm, but submicronparticles equal to or less than 10 μm are difficult to remove. Althoughhigh boiling point substances are often exhausted in the form of vaporfrom driers or the like, these are excited as they enter the treatingapparatus and partly condensed to form a mist. This mist is in minuteparticles approximately 0.3 μm in size, which are not easy to remove bya sticking action. Meanwhile, gaseous high boiling point substances andnoxious and malodorous gas can be removed with relative ease byadsorbing action.

Fine particles minutes in particle size can be electrostaticallyattracted and easily stuck to the powdery adsorbent when the latter ischarged with static electricity as it is mixed into the pneumaticconveyance. Charging of the powdery adsorbent with static electricitycan be economically done through utilization of the kinetic energy ofthe pneumatic conveyance. As pipe there may be used a nonconductive pipesuch as a plastic pipe covered with a conductive material such as metalwith a lead wire connecting it with ground or a voltage source. Theadsorbent is then charged with static electricity as its airborneparticles collide with the inner wall of the pipe and the like. The airpipe may preferably have many bends so that the powdery adsorbent hasincreased chances to collide with the pipe's inner wall. It is, however,also possible to statically charge the powdery adsorbent by ionizing theconveyance air.

Another preferred embodiment enables the noxious and malodorous gascomponents to be obtained in a highly concentrated state. The adsorptionperformance is further enhanced by making the adsorption operation amultistep cascade, using pneumatic conveying and separating means in twoor more steps.

In this instance, the relationship between the concentration and therate of adsorption of the noxious and malodorous gas gives thecharacteristic of the adsorbent in that the higher the concentration,the larger its adsorptive power. Accordingly, by making an adsorbenthave less adsorbate, a higher adsorptive capacity contact with theexhaust gas, for a lower concentration of undesirable gas components inthe exhaust gas, results. This enable the further enhancement of theadsorptive performance of the apparatus as a whole, thereby increasingthe degree of concentration.

Further, according to another preferred embodiment, it is possible toconduct the adsorption during the pneumatic conveying process in thecontacting relationship by supplying the adsorbent at plural positionsusing the single separating means and the single regeneration unit. Thegas cleaning capacity can be further enhanced by bringing the highlyregenerated adsorbent into contact with the gas in a final step.

Further, according to another preferred embodiment, in a process forseparating the powdery adsorbent from the exhaust gas in order to highlyefficiently eliminate the noxious and malodorous gas from the exhaustgas, the front step employs a cyclone and the rear step employs a dustcollecting device consisting of a bag filter, etc. Adsorbent which isslightly contaminated due to adsorption is introduced into the frontprocess of the cyclone, and the powdery adsorbent treated forregeneration in the back process of the dust collecting device isintroduced in the outlet duct which connects the cyclone and the dustcollecting device together.

Countercurrent contacting is preferable in order to bring the exhaustgas and powdery adsorbent into contact for adsorption. But as disclosedin the present invention, equilibrium flow is adopted as a matter ofcourse to make their contact in the pneumatic conveyance, and judgingfrom the parallel relation of the adsorption, a great deal of adsorbentis necessary to provide a high degree of purification to dilute thenoxious and malodorous gas to several ppm or less, as described later.Therefore, in the present invention, under a condition such that thecomponent concentration of the exhaust gas is high, like several hundredppm, primary adsorption is carried out by bringing the exhaust gas intocontact with contaminated adsorbent with which adsorption is partiallyconducted. Next, secondary adsorption is carried out by bringing it intocontact with clean adsorbent for regeneration when the componentconcentration thereof becomes low, like several ten ppm. Namely, by thusmaking plural stepped adsorption operations, it is possible to obtaincleanly treated air from which the noxious and malodorous gas has beeneliminated, from a high concentration to a remarkably low concentrationsuch as less than several ppm. Moreover, by fully utilizing theadsorption capacity of the adsorbent, the amount of use of the adsorbentcan be decreased as much as possible, the facility for the regenerationtreatment can be made small in scale, and an economical exhaust gastreating operation can be achieved.

Zeolites, silica gel, sepiolites, etc., which are inorganic adsorbents,are given as examples of adsorbents to be used for the presentinvention. But hydrophobic zeolite is preferable. This hydrophobiczeolite is a granular powder substance of which the grain diameter isnot more than 300 μm, and preferably not more than 100 μm, is anadsorbing substance which is excellent relative to organic solvents andpolar odors such as ammonia, amines, mercaptans, etc., is chemicallyhigh-silica crystal, and has the characteristics of greatly adsorbingand collecting malodorous components. The characteristic details ofhydrophobic zeolite, etc. are described hereinafter.

According to the present invention, a powdery adsorbent such ashydrophobic zeolite, etc., is mixed with the exhaust gas containing fineparticle dust and noxious and malodorous gas components in a conveyingprocess, such as a pneumatic conveyance, to perform adhesion andadsorption. Accordingly, this system for concentration has a highadsorption efficiency without requiring any special large dustingdevices for pretreatment, like the honeycomb type concentrationapparatus, for the benefit of a simplified and highly economic system ofconcentration.

The process of separation into the adsorbent on which the adsorption andadhesion are made and the purified gas may be performed by suchuniversal methods as a system making use of centrifugal force or bagfilters or the like because of the adsorbent being powdery, for thebenefit of a simplified and sure separation.

Further, according to the present invention, since indicated heating ina small flux of gas for regeneration or direct hating by mixing theadsorbent with a hot blast of high temperature is used, only a smallflux of gas for regeneration is necessary for regeneration of theadsorbent. The regeneration efficiency is improved by raising theheating temperature, and the concentration of the noxious and malodorousgas obtained by the operation for desorption is maintained high. Thus ahighly concentrated noxious and malodorous gas is obtained in this way,permitting the use of an apparatus of compact structure forneutralization of the noxious gas in the deodorization is miniaturizedand simplified by the embodiment of the present invention.

Furthermore, according to the present invention, fine particles arecaptured by getting them stuck on the powdery adsorbent, so the adhesionof the fine particles on the wall surfaces of the apparatus may beprevented. Accordingly, any dust collector, being a highpriced device,may be omitted, and removal of the fine particles from the powderyadsorbent may be performed with an adhering dust treating device whicheffects the heating treatment at several hundred degrees.

In a preferred embodiment, the regenerating step comprises two steps,i.e. a low temperature heating treatment and a high temperature heatingtreatment. The noxious and malodorous gas is separated by desorption inthe first step, and the fine particles are separated by thermaldecomposition in the second step. The preferred embodiment thus achieveshighly efficient and stable exhaust gas treatment.

The two-step treatments with different temperature ranges also ensureextremely safe exhaust gas treatments free from dangers such as ignitionof the noxious and malodorous gas.

Furthermore, since the high temperature gas generated during the exhaustgas neutralizing process if recycled for use as a heating gas for thelow temperature and high temperature heating treatments, the preferredembodiment provides an excellent operating economy.

Further, another preferred embodiment may employ many steps ofcirculating the adsorbent. Thus, at the first step where the noxious andmalodorous gas component concentration is high, the adsorption is madewith the most heavily contaminated adsorbent, and at the second andfollowing steps, where the gas has a successively smaller concentrationof the components, the adsorption is made with a successively lesscontaminated adsorbent. Accordingly, a stable adsorption operation, notinvolving an excessive or an insufficient adsorbing ability, ispossible, thus permitting highly concentrated gas components to becontinuously obtained and efficient desorption to be made during thecontinuous operation for adsorption with a single regeneration unit fordesorption in a multi-step system, for the benefit of a simplifiedapparatus.

Moreover, according to the invention, the adsorbent which has been usedto adsorb, but still has sufficient adsorbing ability, is mixed withhigh concentration gas at the upstream side of the pneumatic conveyingmeans, and the highly regenerated adsorbent is mixed at the downstreamside thereof. Thus, the present invention has an advantage ofeffectively desorbing the high concentration gas by increasing theamount of adsorbent in circulation more than the amount to be processedby a regeneration unit.

According to another preferred embodiment, fine particles can beefficiently electrostatically attracted to the powdery adsorbent mixedinto the exhaust gas, and it is thereby possible to have the collectingperformance remarkably improved.

According to another preferred embodiment, moreover, the regeneratedadsorbent which has been subject to desorption can be conveyed whilebeing cooled, and the adsorbent which will be used in the operation foradsorption in the pneumatic conveying process can be sufficientlycooled, with the result that its adsorption efficiency is high.Moreover, the malodorous gas adsorbed by the powdery adsorbent can beeasily removed by separating the cooling blast and the powderyadsorbent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram of an exhaust gas treating system in carcoating in the prior art;

FIG. 2 is a system diagram of a first embodiment of the presentinvention;

FIG. 3 is a system diagram of a second embodiment of the presentinvention;

FIG. 4 is a system diagram of a third embodiment of the presentinvention;

FIG. 5 is a system diagram of a fourth embodiment of the presentinvention; and

FIG. 6 is an isotherm adsorption diagram of the fourth embodiment shownin FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The apparatus of the first embodiment shown in FIG. 2 is equipped with apneumatic conveying means 1 provided by a pipeline 10 with a blower 9inserted midway along the pipeline 10, separating means 2 provided by abag filter 11, a regeneration unit provided by a ribbon stirrer 12 and adirect firing deodorizer 13.

The apparatus for treating exhaust gas according to the presentinvention corresponds to the apparatus for supplying exhaust gas fromcoating booth 201 shown in FIG. 1 through the exhaust gas pipeline 14and exhausting purified gas after treatment through the pipeline 19. Theabove apparatus is embodied by replacing the wet static dust collector202, the humidity/temperature regulators 203 and 205, the honeycomb typeconcentration apparatus 204, the catalytic oxidization apparatus 206 andthe heat recovering and exchanging device 207 with the means and devicesdescribed hereinafter.

To the inlet side of the pipeline 10, there are connected, respectively,an exhaust gas pipeline 14 for feeding the exhaust gas containing fineparticles and noxious and malodorous gas, for example exhaust gas from acar coating line, and an adsorbent feeding pipeline 15 for feedingadsorbent after it is regenerated at the ribbon stirrer 12 and fed outthereof. The outlet side of the pipeline 10 is connected to the middlepart of a lower chamber 17 of the bag filter 11. The exhaust gas fromthe coating line, which flows through the exhaust gas pipeline 14, andthe hot regenerated powdery adsorbent flowing in the adsorbent feedingpipeline 15, are mixed on the inlet side of the pipeline 10 so as toflow in the pipeline 10 via a blower 9, reaching the bag filter 11 atthe outlet end of the pipeline 10. The powdery adsorbent is rapidlycooled to ordinary temperatures because of it small heat capacity.Accordingly, the noxious and malodorous gas in the exhaust gas from thecoating line is efficiently adsorbed by this powdery adsorbent whilepassing through the pipeline 10. The adhesive dust in the exhaust gasfrom the coating line sticks to the powdery adsorbent, thereby beingseparated from the gas. As a result, the exhaust gas from the coatingline has been purified, with the adhesive dust and the noxious andmalodorous gas having been removed at the point of entry into the lowerchamber 17.

The bag filter 11 is partitioned into an upper chamber 16 and the lowerchamber 17 by a filter assembly 18 formed of a plurality of bag shapedfilter cloths. A pipeline 19 is connected at one end to the top wall ofthe upper chamber 16, and at the other end the pipeline 19 extends tothe car coating booth, for example. On the other hand, to the bottomwall of the lower chamber 17, there is joined a pipeline 21 equippedwith a rotary valve 20. This pipeline 21 has a distal end connected tothe inlet side of the ribbon stirrer 12.

The rotary valve 20 is a feeder having a structure capable of feedingthe powder while a sealing function is performed. It is feasible to usethis system with a double damper substituted for the rotary valve 20,which provides a similar effect as the rotary valve.

The exhaust gas from the coating line and the powdery adsorbent are in amixed state, and are fed into the lower chamber 17 from the pipeline 10.The adsorbent which has the fine particles sticking thereto and thenoxious and malodorous gas adsorbed thereby is collected by the filterassembly 18, and then wiped off by applying back pressure to be broughtdown to the bottom part of the lower chamber 17. The purified exhaustgas from the coating line passes through the filter assembly 18 and isthen exhausted.

The powdery adsorbent which has fallen down to the bottom part is fedinto the ribbon stirrer 12 at a predetermined rate via the rotary valve20. In this way, the separation of the powdery adsorbent on which thefine particles stick and the noxious and malodorous gas is adsorbed fromthe purified gas is continuously performed in the bag filter 11.

The ribbon stirrer 12 is equipped with a horizontal cylindrical tank 22having a jacket for circulating a heating medium formed at acircumferential wall part. A spiral shaped ribbon 23 is stored in thiscylindrical tank 22 and a horizontal shaft 24 is located along thecylindrical center inside the cylindrical tank 22. The horizontal shaft24 is rotatably driven by a motor (not shown in this figure). At thetop, on one end inside of the cylindrical tank 22 (for example, theright end in FIG. 2), is joined the distal end of the pipeline 21, thisone end functioning as the inlet side. In the side wall of the other endof the cylindrical tank 22, (the left end of FIG. 2) there is providedan adsorbent exit hole 25. The exit hole 25 is linked to the inlet ofthe pipeline 10 of the pneumatic conveying means 1 through an adsorbentfeeding pipeline 15, with a valve 26 inserted midway along the pipeline15, and thus this other end functions as the outlet. In the neighborhoodof the portion where the pipeline 21 is connected on the inlet side ofthe cylindrical tank 22, there is provided an air inlet 27. A small fluxof gas such as air, nitrogen, carbonic acid gas or the like, which maybe at an ordinary temperature or heated, is fed to this air inlet 27 asa gas for regeneration.

In this ribbon stirrer 12, as the horizontal shaft 24 turns, the spiralribbon 23 turns with the shaft 24 as the center, and moves along theinside wall of the cylindrical tank 22. By the stirring action of thisribbon 23, the powdery adsorbent fed in from the pipeline 21progressively moves toward the outlet side along the inside wall of thecylindrical tank 22, during which time it contacts and mixes with asmall flux of gas for regeneration fed from the air inlet 27.Simultaneously, it is indirectly heated to 100° to 200° C. by theheating medium inside the jacket. As a result, the adsorbent makescontact with the gas for regeneration under heat, to thereby besubjected to desorption and regeneration. This regenerated adsorbent isreturned to the pipeline 10 of the pneumatic conveying means 1 via theadsorbent feeding pipeline 15 to again provide the adsorbing action.

The noxious and malodorous gas separated by desorption is discharged ina highly concentrated state and in mixture with the small flux of thegas for regeneration which has been used for the regenerating treatmentthrough an exhaust hole 28 provided on the outlet side of thecylindrical tank 22. They are then fed to a direct firing deodorizer 13by a blower 91 interposed between the cylindrical tank 22 and thedeodorizer 13 in an exhaust pipe 29 to be neutralized by combustiontreatment.

A noncombustible adsorbent is advantageous as the powdery adsorbent usedin the embodiment mentioned hereabove, as it involves no hazard of adust explosion and is, therefore, especially advantageous from a safetyviewpoint. Mentioned as an example is hydrophobic zeolite with aparticle diameter of not more than 300 μm, preferably not more than 100μm, as the main component. This hydrophobic zeolite is an excellentadsorbent material to substances with polar malodorous components likeorganic solvents, ammonia, amines and mercaptans. Chemically, it iscrystals of high-silica, and as an adsorbent has a large capacity forcapturing malodorous components by adsorption.

The oxygen atoms present in the silica structure of the hydrophobiczeolite have scarce basicity and have nothing to do with the formationof hydrogen bonds. Hence Si--O--Si bonds in the surface of the zeoliteshow water repellency, not adsorbing the water molecules. Since itstrong adsorbing capacity for polar substances is dependent upon thecation's electrostatic force corresponding to the number of aluminumatoms in the skeleton, the water repellency increases when the number ofAl₂ O₃ in the crystal is decreased and the number of SiO₂ /Al₂ O₃ isincreased, and therefore the water adsorbing capacity can be decreased.The water adsorbing capacity starts decreasing when the number of SiO₂/Al₂ O₃ has reached about 20 cc/100 g, and is decreased close to zerowhen its number has increased to be not less than 80 cc/100 g.Meanwhile, the absorbing capacity for ammonia, amines and mercaptans isincreased when the number of SiO₂ /Al₂ O₃ is in a range of 20-80 cc/100g, preferably 40- 60 cc/100 g.

The ribbon stirrer 12 is used as a means for indirectly heating theadsorbent. Other indirect heating means may be a rotary kiln and otherstructures capable of heating indirectly.

FIG. 3 is a system diagram of a second embodiment of the presentinvention. The apparatus shown in FIG. 3 is equipped with two stepseparating means 2A and 2B realized by bag filters 15A and 15B, two steppneumatic conveying means 1A and 1B realized by pipeline 12A and 12Bwith blowers 11A and 11B inserted midway along the pipelines,respectively, a regeneration unit realized by a ribbon stirrer 12, and acyclone 131.

In this second embodiment, since each construction and arrangements forconnecting each part, such as the bag filters 15A and 15B, the ribbonstirrer 12 and the direct firing deodorizer 13, are respectivelycorrespondent with the construction and arrangement of the bag filter11, the ribbon stirrer 12 and the direct firing deodorizer 13 in thefirst embodiment, the explanation thereof is omitted.

To the inlet side of the pipeline 12A in the first step pneumaticconveying means 1A are connected, respectively, an exhaust gas pipeline14 for feeding in the exhaust gas containing fine particles and noxiousand malodorous gas, for example, exhaust gas from a car coating line,and an adsorbent feeding pipeline 40 for feeding the adsorbent after theadsorbent is regenerated at a cyclone 131 and fed out thereof. Theoutlet side of the pipeline 12A is connected to the middle part of thelower chamber 17 of the first step bag filter 15A. The coating exhaustgas which flows through the exhaust gas pipeline 14 and the regeneratedpowdery adsorbent flowing in the adsorbent feeding pipeline 40 are mixedon the inlet side of the pipeline 12A so as to flow in the pipelines 12Avia a blower 11A, reaching the bag filter 15A at the outlet side of thepipeline 12A. The powdery adsorbent, having a higher temperature thanthe ordinary temperature, is rapidly cooled to the ordinary temperaturedue to its small heat capacity. Accordingly, the noxious and malodorousgas in the coating exhaust gas are efficiently adsorbed by this powderyadsorbent while passing through inside the pipeline 12A. The fineparticles in the coating exhaust gas also stick to the powderyadsorbent.

As a result, the exhaust gas is purified, with the fine particles andthe noxious and malodorous gas being removed at the point of entry intothe lower chamber 17.

The outlet side of the pipeline 12B of the second step pneumaticconveying means 1B is linked to the middle part of the lower chamber 17of the second step bag filter 15B. The purified gas flowing in thepipeline 19, after being separated from the adsorbent by the first stepbag filter 15A, and the regenerated powdery adsorbent fed in at apredetermined rate by virtue of the rotary valve 26 through theadsorbent feeding pipeline 15, are mixed on the inlet side of thepipeline 12B and flow in the pipeline 12B via a blower 11B, reaching thesecond step bag filter 15B from the outlet side of the pipeline 12B. Thepowdery adsorbent, which has been heated to a high temperature in theribbon stirrer 12, is rapidly cooled to the ordinary temperature due toits small heat capacity at the point when it is mixed with the purifiedgas. Accordingly, the noxious and malodorous gas remaining in thepurified gas is adsorbed by the powdery adsorbent with high efficiencywhile passing through the inside of the pipeline 12B. As a result, thepurified gas has a still higher degree of purification at the time whenit is fed into the lower chamber 17.

The second step bag filter 15B has the same structure as theaforementioned first step bag filter 15A and provides the same action.Therefore, its detailed explanation is omitted.

The purified gas containing the adsorbent, which has been fed into thelower chamber 17 from the pipeline 12B, is separated into the adsorbentand the purified gas by the filter assembly 18, and the purified gas isthen discharged to the atmosphere. The powdery adsorbent which has beencaptured by the filter assembly 18 and has fallen down to the bottom isfed in on an inlet side of a transport pipeline 54 at a predeterminedrate via a rotary valve 20.

The transport pipeline 54 extends between the part beneath the secondstep bag filter 15B and the first step pneumatic conveying means 1A. Theinlet end part by the second step bag filter 15B is connected to aforced draft fan 41, while the outlet end part by the first steppneumatic conveying means 1A is connected to a cyclone 131. Theadsorbent fed out via the rotary valve 20 at the predetermined rate isprovided to the transport pipeline 54 near its connection to thedischarge side of the fan 41 so as to be fed to the cyclone 131, carriedby a current for conveying, for example compressed air, discharged bythe fan 41.

The adsorbent which has fallen downward and accumulated at the bottom ofa body 131A of the cyclone 131 is fed out at a predetermined rate via arotary valve 33 to be fed into the pipeline 12A of the first steppneumatic conveying means 1A. This cyclone 131 may be omitted, as thecase may be. In that instance, the mixed current of adsorbent and theatmosphere carried by the transport pipeline 54 should be directly fedto the first step pneumatic conveying means 1A.

FIG. 4 is a system diagram of an exhaust gas treatment apparatus showinga third embodiment of the present invention. The apparatus shown in FIG.4 comprises adsorption pneumatic conveying means 1, separating means 2,low temperature heat treating means 3, high temperature heat treatingmeans 4, adsorbent feeding means 5, and neutralizing and deodorizingtreating means consisting of a first treating means 6 and a secondtreating means 7.

The adsorption pneumatic conveying means 1 comprises gas carrying lines9A and 9B in which first and second adsorbent feeder nozzles 13A and 13Bare respectively installed and through which an exhaust gas G, such as apaint exhaust gas, is transported. A first pneumatic conveying line 10Aconsists essentially of a pipeline 12A having a blower 11A. The exhaustgas G is pneumatically transported and is mixed with powdery adsorbentinjected into the gas carrying line 9A from the first adsorbent feedernozzle 13A, and flows into the downstream gas carrying line 9B where theexhaust gas G is mixed with adsorbent injected from the second adsorbentfeeder nozzle 13B, the exhaust gas G then being direct furtherdownstream. The exhaust gas G, containing the fine particles and thenoxious and malodorous gas, is thus mixed with adsorbent, for example,hydrophobic zeolite, so that, during pneumatic conveyance, the fineparticles are made to adhere to the surfaces of the zeolites while thenoxious and malodorous gas is adsorbed into the pores of the zeolite.

The separating means 2 comprises a first dust collector realized by afirst cyclone 14A, a second dust collector realized by the first bagfilter 15A, a first receiver 16A, and two screw feeders 17A and 17B.

The gas carrying line 9B is centrally installed in the cylindrical bodyof the first cyclone 14A in a concentric relationship therewith, the gascarrying line 9B serving as an inner cylinder for exhaust. Attached tothe upper part of the cylindrical wall of the body is the outlet end ofthe gas carrying line 9A, while in the bottom of the body there isprovided an outlet at which a rotary valve 20 is installed. The firstbag filter 15A consists of two chambers, an upper chamber and a lowerchamber, separated by a filter assembly 18 comprising a plurality ofbag-shaped filter cloths. In the top wall of the upper chamber, there isa discharge port 19, and to the upper part of the sidewall of the lowerchamber is attached the outlet end of the gas carrying line 9B. In thebottom of the lower chamber there is provided an outlet at which arotary valve 21A is installed.

The first receive 16A is disposed beneath the first cyclone 14A and thefirst bag filter 15A. Attached to the top wall of the receiver containerare pipelines extending from the rotary valves 20 and 21A, while thebottom wall of the container is provided with an outlet. The screwfeeders 17A and 17B are each constructed with a body in which a screw isrotatably mounted and which is provided with a charge port and adischarge port, the charge port being connected to the outlet of thereceiver 16A via the pipeline. The discharge ports are respectivelyconnected to halfway points along the pipeline 12A and a pipeline 12Bdescribed hereinafter by respective pipelines, in which pipeline rotaryvalves 22A and 22B are installed.

The rotary valves 20, 21A, 22A, and 22B are identical in construction.Each valve is a feeder having a structure capable of feeding the powderwhile a sealing function is performed. Double dampers having the samefunction can be used instead of the rotary valve.

The separating means 2 operates in the following manner. The fluidstream flowing through the gas carrying line 9A, i.e. the exhaust gas Gmixed with the powdery adsorbent, flows into the first cyclone 14A in adirection parallel to a tangent to the cylindrical wall thereof, andspirals downward along the inner wall of the cylindrical body. Whilethis is happening, the adsorbent, laden with the fine particles and thenoxious and malodorous gas, is forced toward the wall by centrifugalforce so that the adsorbent is separated from the exhaust gas G,purified to a certain level, and falls downward along the wall. In themeantime, the exhaust gas G separated from the adsorbent is drawn intothe gas carrying line 9B from below, is mixed with the regeneratedadsorbent injected from the adsorbent feeder nozzle 13B, and is fed intothe lower chamber of the first bag filter 15A from above. On the otherhand, the adsorbent, which has fallen downward and which still retainsthe ability to perform as an adsorbent, is fed into the first receiver16A by the rotary valve 20. The fluid stream that has flown into thelower chamber of the first bag filter 15A, i.e. the exhaust gas G thatcontains unremoved adsorbent, is drawn across the filter assembly 18,which collected the adsorbent laden with fine particles and the noxiousand malodorous gas. A negative pressure is applied to the filterassembly 18 to knock off the collected adsorbent, which then fallsdownward to the bottom of the chamber. On the other hand, the purifiedexhaust gas G is discharged to the atmosphere, or recovered, through thedischarge port 19.

The powdery adsorbent that has fallen to the bottom of the chamber isfed through the rotary valve 21A into the first receiver 16A, where itis mixed with the adsorbent delivered through the rotary valve 20. Theadsorbent collected in the first receiver 16A is separated between thescrew feeders 17A and 17B, and is delivered through the rotary valves22A and 22B, one for mixing the adsorbent with the air stream flowingthrough the pipeline 12A and the other for mixing the adsorbent with thehot blast stream flowing through the pipeline 12B described hereinafter.In this manner the separating means 2 separates the adsorbent and theexhaust gas, fed in the form of a mixture from the adsorption pneumaticconveying means 1, with most of the separated adsorbent being deliveredto the low temperature heat treating means 3 and a portion of theadsorbent being returned to the adsorption pneumatic conveying means 1so as to carry out the adhering and adsorbing treatment.

The low temperature heat treating means 3 comprises a second pneumaticconveying line 10B, consisting essentially of the pipeline 12B in whichis installed a blower 11B, a second cyclone 14B, a second bag filter15B, and a second receiver 16B. The pipeline 12B of the second pneumaticconveying line 10B is connected at its inlet end to a pipeline 24carrying a hot blast stream and at a halfway point, near the suctionside of the blower 11B, to a pipeline 25 carrying an ordinarytemperature air stream. The outlet end of the pipeline 12B is connectedto the upper part of the cylindrical body of the second cyclone 14B. Atemperature control valve 127 is installed in the pipeline 25. Thesecond cyclone 14B, the second bag filter 15B, and the second receiver16B are equivalent in construction and arrangement to the first cyclone14A, the first bag filter 15A, and the first receiver 16A in theseparating means 2, and therefore detailed descriptions thereof areomitted herein. It should be noted, however, that a rotary valve 23Bdisposed on the outlet side of the second receiver 16B is connected viaa pipeline to a halfway point of a pipeline 12C, carrying a hot blaststream and described hereinafter.

The low temperature heat treating means 3 operates in the followingmanner. The adsorbent, fully laden with fine particles and the noxiousand malodorous gas, is delivered at a predetermined rate from the screwfeeder 17B to the pipeline 12B of the second pneumatic conveying line10B, where the adsorbent is mixed into the pneumatic stream, which ismaintained at a low temperature, for example at 300° C., by the actionof the temperature control valve 127. The resulting gas-solid mixture,with its temperature now lowered to about 200° C., is drawn into thesecond cyclone 14B. In the pipeline 12B, because the adsorbent is heatedto about 200° C., the noxious and malodorous gas adsorbed herein is nowdesorbed. On the other hand, the fine particles adhering to theadsorbent are left adhered to the adsorbent, because the temperature islower than their thermal decomposition temperature (400° to 500° C.).The flow rate of the pneumatic stream in the pipeline 12B can be as slowas 3 to 10m³ /hour to accomplish the above desorption, as compared withthe flow rate of 100m³ /hour for the exhaust gas G flowing in the gascarrying line 9A. As a result, exhaust gas in a state of highconcentration is delivered for treatment in the low temperature heattreating means 3. Therefore, the low temperature heat treating means 3,including the second bag filter 15B, can be accomplished by asmall-sized apparatus.

The adsorbent, having been separated from the concentrated exhaust gasin the second cyclone 14B and fallen downward, is delivered to thesecond receiver 16B. On the other hand, the highly concentrated exhaustgas separated from the adsorbent is drawn into the lower chamber of thesecond bag filter 15B, where the remaining adsorbent is separated fromthe highly concentrated exhaust gas. The adsorbent that has fallendownward is fed through a rotary valve 21B into the second receiver 16B,while the highly concentrated exhaust gas passed through the filterassembly 18 is discharged through the discharge port 19 provided in thetop wall of the upper chamber and introduced into the first treatingmeans 6, described hereinafter.

The adsorbent collected in the second receiver 16B, still laden withfine particles, is delivered through the rotary valve 23B for mixinginto a hot pneumatic stream flowing through a pipeline 12C of a thirdpneumatic conveying line 10C described hereinafter. As described, in thelow temperature heat treating means 3, the adsorbent delivered from theseparating means 2 is heated to a low temperature of 120° C. to 250° C.for the desorption of the noxious and malodorous gas and the noxious andmalodorous gas separated from the adsorbent is introduced into the firsttreating means 6, whereas the adsorbent is delivered to the hightemperature heat treating means 4.

The high temperature heat treating means 4 comprises a third pneumaticconveying line 10C, consisting essentially of a pipeline 12C in which ablower 11C is installed, a third cyclone 14C, a third bag filter 15C anda third receiver 16C. These component elements are equivalent inconstruction and arrangement to the second pneumatic conveying line 10B,the second cyclone 13C, the second bag filter 15B, and the secondreceiver 16B in the low temperature heat treating means 3, and thereforedetailed descriptions thereof are omitted herein.

The operation of the high temperature heat treating means 4 will now bedescribed. The adsorbent laden with fine particles is delivered from thesecond receiver 16B to the pipeline 12C of the third pneumatic conveyingline 10C, where the adsorbent is mixed into the pneumatic stream,maintained at a high temperature, for example, at 600° C., and thusheated to 350° to 500° C. A pneumatic stream from a pipeline 26, whichits temperature controlled by a temperature control valve 128, is mixedwith the hot pneumatic stream of about 800° C. flowing in the pipeline25 so that the hot pneumatic stream in the pipeline 12C is maintained ata constant temperature. The gas-solid mixture containing the adsorbentis carried in the pipeline 12C and drawn into the third cyclone 14C. Inthe process, the fine particles adhered to the adsorbent are thermallydecomposed by the high temperatures in the pipeline 12C and the thirdcyclone 14C and removed from the adsorbent, thus regenerating theadsorbent. Most of the regenerated adsorbent is separated in the thirdcyclone 14C and fed from the bottom thereof in the third receiver 16C.On the other hand, the exhaust gas separated from the adsorbent is drawninto the lower chamber of the third bag filter 15C, where the remainingadsorbent and exhaust gas are completely separated, the adsorbent thenfalling downward and being fed by a rotary valve 21C into the thirdreceiver 16C. The exhaust gas that has passed through the filterassembly 18 of the bag filter 15C is discharged through the dischargeport 19 provided in the top wall of the upper chamber and introducedinto the second treating means 7 described hereinafter.

The regenerated adsorbent collected in the third receiver 16C isdelivered by a rotary valve 23C for mixing it into a pneumatic streamflowing through a pipeline 12D of the fourth pneumatic conveying line10D in the adsorbent feeding means 5 described hereinafter. Asdescribed, in the high temperature heat treating means 4, the adsorbentdelivered from the low temperature heat treating means 3 is heated to ahigh temperature of 350° to 600° C. to thermally decompose, and thusdesorb, the mists and high-boiling point substances. The regeneratedadsorbent is then delivered to the adsorbent feeding means 5, whereasthe exhaust gas generated during the thermal decomposition process isintroduced into the second treating means 7.

The adsorbent feeding means 5 comprises the fourth pneumatic conveyingline 10D, consisting essentially of the pipeline 12D in which a blower11D is installed, a fourth cyclone 14D, a fourth bag filter 15D, afourth receiver 16D, and a fifth pneumatic conveying line 10E consistingessentially of a pipeline 12E in which a blower lie is installed. Thefourth pneumatic conveying line 10D, the fourth cyclone 14D, the fourthbag filter 15D, and the fourth receiver 16D are equivalent inconstruction and arrangement to the second pneumatic conveying line 10B,the second cyclone 14B, the second bag filter 15B, and the secondreceiver 16B in the low temperature treating means 3, except that thecarrier fluid is atmospheric air. Therefore, detailed descriptions ofthese component elements are omitted herein. The fourth and fifthpneumatic conveying lines 10D and 10E transport ordinary temperatureatmospheric air drawn through the respective blowers 11D and 11E, andthe outlet end of the pipeline 12E of the fifth pneumatic conveying line10E is connected to the adsorbent feeder nozzle 13B installed inside thegas carrying line 9B.

The operation of the adsorbent feeding means 5 will now be described.The regenerated adsorbent of high temperature, collected in the thirdreceive 16C, is fed by the rotary valve 23C in the pipeline 12D, wherethe adsorbent is cooled by mixing it with the ordinary temperature airstream, the resulting air-solid mixture then being drawn into the fourthcyclone 14D. In the cyclone 14D, the further cooled and regeneratedadsorbent and the air are separated, and the air is drawn into the lowerchamber of the fourth bag filter 15D while the regenerated adsorbent isforced downward and collected in the fourth receiver 16D. The air drawninto the lower chamber contains fine regenerated adsorbent leftunremoved in the fourth cyclone 14D. In the fourth bag filter 15D, theremaining adsorbent and the air are completely separated, and the air isdischarged to the atmosphere through the discharge port 19, while theregenerated adsorbent is forced downward and fed by the rotary valve 21Ainto the fourth receiver 16D. The regenerated adsorbent collected in thefourth receiver 16D is cooled and then fed through a rotary valve 23Dinto the pipeline 12E. The adsorbent is mixed with the ordinarytemperature air stream in the pipeline 12E, which carries the adsorbentto the adsorbent to the adsorbent feeder nozzle 13B for injection intothe gas carrying line 9B. Thus, in the adsorbent feeding means 5, theregenerated adsorbent of high temperature, fed from the high temperatureheat treating means 4, is cooled in the fourth pneumatic conveying line10D, the fourth cyclone 14D, and the fourth bag filter 15D, and thecooled and regenerated adsorbent separated from the air is returnedthrough the fifth pneumatic conveying line 10E to the adsorbentpneumatic conveying means 1 where the adsorbent is reused for adsorbingthe exhaust gas.

The fist treating means 6 comprises a cooler 29 and a solvent collectingdevice 30. The cooler 29 consists essentially of a heat exchanger, whichis, for example, of a gas-to-liquid type, wherein the inlet end of a gasline is connected via a pipeline 31 to the discharge port 19 of thesecond bag filter 15B, while cooling water is circulated through aliquid line. The solvent collecting device 30 is realized by, forexample, an adsorption type solvent collecting device, in whichactivated charcoal is used as an adsorbent. The inlet end of the device30 is connected via the pipeline 31 to the outlet end of the gas line inthe cooler 29.

The concentrated noxious and malodorous gas discharged from thedischarge port 19 of the second bag filter 15B is cooled through thecooler 29 and fed into the adsorption type solvent collecting device 30where the gas is adsorbed on activated charcoal. The noxious andmalodorous gas is thus collected by adsorption in the first treatingmeans 6.

The second treating means 7 comprises an oxidative cracker 33. Theoxidative cracker 33 is constructed, for example, from a direct firingcombustion furnace with a combustion burner 34 installed therein. Thegas inlet port of the furnace is connected via a pipeline 32 to thedischarge port 19 of the third bag filter 15C, while the exhaust portthereof is connected to a flue as well as the inlet end of the pipeline24.

The exhaust gas discharged from the discharge port 19 of the third bagfilter 15C is drawn through the pipeline 32 into the direct firingcombustion furnace 33, where the exhaust gas is burned and neutralized.The neutralized exhaust gas is discharged to the atmosphere from theflue, while a portion thereof is drawn into the pipeline 24 and used ashot carrier gas in the second pneumatic conveying line 10B of the lowtemperature heat treating means 4 as well as in the third pneumaticconveying line 10C of the high temperature heat treating means 5, aspreviously described. In this manner, the second treating means 7neutralizes the exhaust gas that was thermally decomposed and separatedin the high temperature heat treating means 4, and recycles the hightemperature gas, generated during the neutralizing and deodorizingprocess, for use as low temperature gas for the low temperature heattreating means 3 and also as high temperature gas for the hightemperature heat treating means 4. For the oxidative cracker 33, acatalytic oxidization device may be used instead of the direct firingcombustion furnace.

In this embodiment, the neutralizing and deodorizing treatment of theexhaust gas is accomplished by a two-step process, i.e. by the firsttreating means 6 and the second treating means 7. As an alternativearrangement, the first treating means 6 may be omitted, and the pipeline32 may be further extended to connect to the discharge port 19 of thesecond bag filter 15B so that the exhaust gas separated in both the lowtemperature heat treating means 3 and the high temperature heat treatingmeans 4 can be simultaneously treated. for neutralizing and deodorizingin the second treating means 7.

Also, in the high temperature heat treating means 4, indirect heatingusing a rotary kiln or a ribbon mixer may be performed.

In this embodiment, all of the powdery adsorbent treated by lowtemperature heating is subject to high temperature heating treatment.However, if the amount of the fine particles is extremely smaller thanthat of the gas, just a part of the powdery adsorbent treated by lowtemperature heating may be subject to high temperature heatingtreatment.

The adsorbing and adhering operation of the adsorbent pneumaticconveying means 1 of FIG. 4 will be described below. At the point wherethe first adsorbent feeder nozzle 13A is installed in the gas carryingline 9A, the exhaust gas is high in its content of fine particles andnoxious and malodorous gas components, and these high concentrationcomponents need to be adsorbed and adhered as much as possible by thepowdery adsorbent. The adsorbing and adhering process is performed untilthe concentration of each component is lowered, for example, from 100ppm to 20 ppm. At this step, since the adsorbing and adhering process isperformed for high concentration components, the adsorbent does not needto be regenerated to perform the job; an adsorbent lightly laden withcontaminants can be safely reused for the process. On the other hand, atthe point where the second adsorbent feeder nozzle 13B is installed inthe gas carrying line 9B, the component concentration has been lowered,for example, to 20 ppm, and further adsorbing and adhering is requiredto be performed for such low concentration components. Therefore,purified and regenerated adsorbent is supplied from the adsorbentfeeding means 5 to perform highly effective adsorbing and adhering. As aresult, from the nozzles 13A to 13B, the exhaust gas of 20 ppmconcentration, for example, can be purified to a virtually harmlessstate of 1 ppm.

The screw feeders 17a and 17b used in this embodiment may be replaced byother quantitative feeders such as spiral feeders or vibrating feeders.Also, double dampers may be used instead of rotary valves. The receivers16B, 16C, and 16D are not essential components, but may be omitted.

When purifying the high concentration noxious and malodorous gas in thepresent invention, the adsorbent which is separated in the dustcollecting apparatus 15A or is mixed after being separated by thecyclone 14A and the dust collecting apparatus 15A may be used.

Further, in the apparatus shown in FIG. 4, a first pneumatic conveyingpath 10A is formed as a pneumatic conveying means for charging.

The first pneumatic conveying path 10A, as the pneumatic conveying meansfor charging, has a blower 11A and a pipeline 12A as element members.The pipeline 12A is wholly or mostly composed or nonconductive materialssuch as ceramics and plastics, and its outer periphery is covered with aconductive material 135 such as metal mesh. The conductive material 135is grounded or has its potential adjusted to zero. This pipeline 12A isformed such that the powdery adsorbent, such as hydrophobic zeolite, ispneumatically conveyed therethrough. This adsorbent collides with forcewith the pipeline's inner wall with simultaneous sliding contact withthe air flow, this resulting in the generation of static electricitythrough friction and the adsorbent flowing therethrough being chargedthereby.

It is preferable to use a bent pipe having many bends as the pipeline12A to facilitate collision of the adsorbent.

This first pneumatic conveying path 10A conveys the adsorbentpneumatically as it is mixed into the air stream flowing through thepipeline 12A, and simultaneously causes it to be charged statically. Thestatically charged powdery adsorbent gushes out through the first nozzle13A for the adsorbent.

Although in the third embodiment there is shown an example in whichkinetic energy is used for electrostatically charging the adsorbentbeing pneumatically conveyed, it is also possible to directly charge theadsorbent by mixing ionized air into the adsorbent. Since, however, theequipment cost is bound to be quite high, it may as well be possible tocharge part of the adsorbent to be supplied to the pneumatic conveyingpart for adsorption and supply it to the pneumatic conveying part foradsorption, preferably to the cyclone 14A.

FIG. 5 schematically illustrates an apparatus for treating exhaust gasof a fourth embodiment of the present invention. The apparatus of FIG. 5includes dust collecting means consisting of plural, for example, four,dust collecting means 101, 102, 103 and 10n, regenerating meansconsisting of low temperature heat treating means 3 and high temperatureheat treating means 4, adsorbent supplying means (adsorbent supply unit)5, neutralizing and deodorizing means consisting of first treating means6 and second treating means 7, and pneumatic conveying means consistingof plural, for example, two, intermediate pneumatic conveying means 10Aand 10F.

In this embodiment, since the construction and operation of the lowtemperature heat treating means 3, the high temperature heat treatingmeans 4, the adsorbent supply unit 5, the first treating means 6 and thesecond treating means 7 are the same as those mentioned in the thirdembodiment, the explanations thereof are omitted. Further, detaileddrawings of such means as mentioned above are omitted by using referencenumber 35, which shows a regeneration device consisting of means 3-7.

The first dust collecting means 101 includes a gas conduit 9A throughwhich gas G, such as a coating exhaust gas, passes, a first adsorbentnozzle 13A disposed in the gas conduit 9A, and a first cyclone separate14A1 for collecting adsorbent. Incombustible powdery adsorbent injectedfrom the first adsorbent nozzle 13A is mixed with the exhaust gas Gflowing in the gas conduit 9A, and the exhaust gas G containing thesolid is supplied into the first cyclone separator 14A1.

In the first cyclone separate 14A1, an exhaust cylinder isconcentrically disposed on the center of a cylindrical body. One end ofthe gas conduit 9A is connected to the upper portion of the wall of thecylindrical body, and a rotary valve 20A is attached to an outletextending from the bottom wall of the cylindrical body.

Operation of the first dust collecting means 101 is describedhereinafter. The gas G mixed with the powdery adsorbent flows throughthe gas conduit 9A into the cylindrical body of the first cycloneseparate 14A1 and spirally falls along the inner wall of the cylindricalbody. While the exhaust gas G flows through the gas conduit 9A and thecylindrical body of the first cyclone separate 14A1, the noxious andmalodorous gas in the exhaust gas G is efficiently adsorbed by theadsorbent mixed with the exhaust gas G, which has been partly purified,by means of centrifugal force, further falls along the inner wall of thefirst cyclone separator 14A1, and is exhausted into a conduit 12B viathe rotary valve 20A. The partly purified exhaust gas G, on the otherhand, flows upward into the exhaust cylinder in the center of the firstcyclone separator 14A1 and is mixed with the powdery adsorbent injectedfrom a second adsorbent nozzle 13B disposed in the exhaust cylinder. Theadsorbent falls along the inner wall and is exhausted into the conduit12B via the rotary valve 20A.

The second dust collecting means 102 includes a gas conduit 9B and asecond cyclone separator 14A2. The gas conduit 9B and the second cycloneseparator 14A2 have virtually the same structures as the gas conduit 9Aand the first cyclone separator 14A1, respectively, so the samereference numbers are given to corresponding parts. The gas conduit 9Bconnects the exhaust cylinder of the first cyclone separator 14A1 to anexhaust gas inlet on the upper portion of the wall of the second cycloneseparator 14A2. The second dust collecting means 102 is accordinglycoupled with the first dust collecting means 101 in series.

Operation of the second dust collecting means 102 is describedhereinafter. The exhaust gas G mixed with the powdery adsorbent in theexhaust cylinder of the first dust collecting means 101 is furtherpurified by the adsorbent while flowing through the gas conduit 9B. Thefurther purified exhaust gas G is then separated from the adsorbent,which has adsorbed the noxious and malodorous gas in the exhaust gas G,by means of centrifugal force in the second cyclone separator 14A2. Theexhaust gas G flows upward into an exhaust cylinder disposed on thecenter of the second cyclone separator 14A2 and is mixed with powderyadsorbent injected from a third adsorbent nozzle 13C disposed in theexhaust cylinder, while the adsorbent falls along the inner wall of thesecond cyclone separator 14A2, is exhausted into a conduit 12A of thefirst intermediate pneumatic conveying means 10A via the rotary valve20B, and then is injected from the first adsorbent nozzle 13A.

The third dust collecting means 103 includes a gas conduit 9C and athird cyclone separator 14A3. The gas conduit 9C and third cycloneseparator 14A3 have virtually the same structures as the gas conduit 9Aand the first cyclone separator 14A1, respectively, so the samereference numbers are given to corresponding parts. The gas conduit 9Cconnects the exhaust cylinder of the second cyclone separator 14A2 to agas inlet on the upper portion of the wall of the third cycloneseparator 14A3. The second dust collecting means 103 is accordinglycoupled with the second dust connecting means 102 in series.

Operation of the third dust collecting means 103 is describedhereinafter. The exhaust gas G mixed with the powdery adsorbent in theexhaust cylinder of the second dust collecting means 102 is furtherpurified by the adsorbent while flowing through the gas conduit 9C. Thefurther purified exhaust gas G is then separated from the adsorbent,which has adsorbed the noxious and malodorous gas in the exhaust gas G,by means of centrifugal force in the third cyclone separator 14A3. Theexhaust gas G flows upward into an exhaust cylinder disposed in thecenter of the third cyclone separator 14A3 and is mixed with powderyadsorbent injected from a fourth adsorbent nozzle 13D disposed in theexhaust cylinder, while the adsorbent falls along the inner wall of thethird cyclone separator 14A3, is exhausted into a conduit 12F of thefirst intermediate pneumatic conveying means 10A via the rotary valve20C, and is then injected from a first adsorbent nozzle 13A.

The last dust collecting means 10n includes a gas conduit 9D thoughwhich the gas exhaust G passes, similar to the gas conduits 9A, 9B and9C, and a first bag filter 15A for collecting adsorbent like the first,the second and the third cyclone separators 14A1, 14A2 and 14A3.

The first bag filter 15A is divided into two chambers, that is, an upperchamber and a lower chamber, by a filter assembly 18 formed of aplurality of bag shaped filter cloths. An exchange port 19 is formed onthe top of the upper chamber. The outlet end of the gas conduit 9D isconnected to the upper portion of the side wall of the lower chamber,and the inlet end of the gas conduit 9D is connected to the exhaustcylinder of the third cyclone separator 14A3. A rotary valve 21A isattached to an outlet extending from the bottom wall of the lowerchamber. The last dust collecting means 10n is accordingly coupled withthe third dust collecting means 103 in series.

The operation of the last dust collecting means 10n is describedhereinafter. The exhaust gas G mixed with the powdery adsorbent in theexhaust cylinder of the third dust collecting means 103 is furtherpurified by the adsorbent while flowing through the gas conduit 9D. Theexhaust gas G containing the adsorbent is then supplied to the lowerchamber of the first bag filter 15A. The purified exhaust gas G passesthrough filter assembly 18 and is exhausted to the atmosphere via theexchange port 19 or is collected, while the adsorbent is collected bythe filter assembly 18, is dropped to the bottom of the lower chamber bymeans of a reverse pressure, is exhausted into a conduit 12G via therotary valve 21A, and is then injected from the third adsorbent nozzle13C.

FIG. 6 is an isotherm adsorption diagram showing the relationshipbetween the concentration of gas components and the adsorbed quantity.FIG. 6 is correspondent with the adsorbing operation of the fourthembodiment as shown in FIG. 5.

This relationship is described according to FIG. 5 and FIG. 6. Theconcentration P of gas components to be treated in the exhaust gas G isassumed to be 100 ppm at an inlet of the gas conduit 9A. When the gasexhaust G is brought into contact with adsorbent (adsorbed quantity Q4)injected from the first adsorbent nozzle 13A, the gas components areadsorbed in the adsorbent and the quantity adsorbed in the adsorbentincreased to Q5.

The adsorbent (adsorbed quantity Q5) is transferred to the regenerationdevice 35 and regenerated by the heat treatment as the cleanest powderyadsorbent of the smallest adsorbed quantity Q1. The cleanest adsorbentis cooled and supplied into a bag filter 15A of the last dust collectingmeans 10n to be brought into contact with the purified exhaust gas Gcontaining only a small amount of the target gas components. Theadsorbent increases its adsorption quantity to Q2 through thisadsorption and is supplied to a third cyclone separator 14A3 of thethird dust collecting means 103.

The adsorbent increases the adsorbed quantity from Q2 to Q3 throughadsorption in the third cyclone separator 14A3, and is then supplied tothe second cyclone separator 14A2 of the second dust collecting means102. The adsorbent then increases the adsorbed quantity from Q3 toQ4through the adsorption in the second cyclone separator 14A2, and isthen supplied to the gas conduit 9A connected to the first dustcollecting means 101.

As described above, the adsorbent used and separated in the second,third, and last dust collecting means 102, 103 and 10n is recycled tothe prior dust collecting means 101, 102, and 103, respectively, whereasthe adsorbent used and separated in the first dust collecting means 101is regenerated and recycled to the last dust collecting means 10n. Thepowdery adsorbent is thus virtually in countercurrent contact with theexhaust gas G, and has a high adsorption efficiency. The regeneratingmeans can efficiently regenerate the tainted adsorbent, and the sameamount of adsorbent is brought into contact with the exhaust gas G inall of the dust collecting means 101 to 10n.

Further, in regenerating powdery adsorbent by heat treatment, in thepresent invention, the powdery adsorbent may be indirectly heated byindirect heating means, or the gas for heating may be brought intocontact directly with the powdery adsorbent as the heat treatment.

As described herein, the present invention may be used not only fortreating exhaust gas generated in an automobile coating process,printing process, steel pipe manufacturing process, etc., but also invarious specific areas relevant to other purposes.

I claim:
 1. An apparatus for treating an exhaust gas containingparticles that comprise organic compounds as a component and a noxiousand malodorous gas, comprising:a powdery adsorbent; a means for mixingthe powdery adsorbent with an exhaust gas so as to adhere particles ofthe exhaust gas to the powdery adsorbent and so as to have the powderyadsorbent adsorb a noxious and malodorous gas component of the exhaustgas and for separating the powdery adsorbent having the particlesadhered thereto and the noxious and malodorous gas adsorbed thereby fromthe exhaust gas after the exhaust gas has been at least partiallypurified; a means for regenerating the powdery adsorbent that has beenseparated, said means for regenerating being connected with said meansfor mixing and separating, and said means for regenerating comprising afirst heating means for heating the powdery adsorbent at a firsttemperature sufficient to have the noxious and malodorous gas desorbedfrom the powdery adsorbent and a second heating means for heating thepowdery adsorbent treated by said first heating means at a secondtemperature sufficient to thermally decompose the particles, wherein thefirst temperature is substantially lower than the second temperature;and means connected between said means for mixing and separating andsaid means for regenerating for conveying the regenerated powderyadsorbent from said means for regenerating to said means for mixing andseparating.
 2. The apparatus of claim 1, wherein said first heatingmeans is constructed and arranged for heating the powdery adsorbent atthe first temperature, from about 120° C. to about 250° C., and saidsecond heating means is constructed and arranged for heating the powderyadsorbent at the second temperature, from about 350° C. to about 600° C.3. The apparatus of claim 1, wherein at least one of said first heatingmeans and said second heating means comprises means for heating thepowdery adsorbent by mixing the powdery adsorbent with a heated gas forregeneration of the powdery adsorbent.
 4. The apparatus of claim 1,wherein the powdery adsorbent is a hydrophobic zeolite powder.
 5. Theapparatus of claim 1, wherein said means for mixing and separatingcomprises a cyclone for separating powdery adsorbent from the exhaustgas and a bag filter for separating powdery adsorbent from the exhaustgas.
 6. The apparatus of claim 1, wherein said means for mixing andseparating comprises a bag filter for separating the powdery adsorbentfrom the exhaust gas.
 7. The apparatus of claim 1, wherein said meansfor regenerating comprises a plurality of cyclones and a plurality ofbag filters, with each of said cyclones being connected with arespective one of said bag filters, and the pairs of cyclones and bagfilters being connected in series.
 8. The apparatus of claim 1, whereinsaid means for mixing and separating comprises a means forelectrostatically charging the powdery adsorbent conveyed to said meansfor mixing and separating by said means for conveying.
 9. The apparatusof claim 1, and further comprising:a means for detoxifying anddeodorizing the noxious and malodorous gas desorbed by said means forregenerating, said means for detoxifying and deodorizing comprising atleast one of an adsorption collection device and an oxidativedegradation device.
 10. An apparatus for treating an exhaust gascontaining fine particles that comprise organic compounds as a componentand a noxious and malodorous gas, comprising:a powdery adsorbent; ameans for mixing the powdery adsorbent with an exhaust gas so as toadhere particles of the exhaust gas to the powdery adsorbent and so asto have the powdery adsorbent adsorb a noxious and malodorous gascomponent of the exhaust gas; a means for separating powdery adsorbenthaving the particles adhered thereto and the noxious and malodorous gasadsorbed thereby from the exhaust gas after the exhaust gas has been atleast partially purified, said means for separating comprising a firstdust separator connected in series with a second dust separator, saidfirst dust separator being connected to said means for mixing in orderto receive mixed powdery adsorbent and exhaust gas from said means formixing, and said second dust separator being connected with said meansfor mixing in order to supply powdery adsorbent separated by said seconddust separator to said means for mixing; a means for regenerating thepowdery adsorbent separated by said first dust separator by heating thepowdery adsorbent so as to remove the noxious and malodorous gas and thefine particles therefrom so as to obtain a regenerated powderyadsorbent; and a means for conveying the regenerated powdery adsorbentfrom said regenerating means to said second dust separator.
 11. Anapparatus for treating an exhaust gas containing particles that compriseorganic compounds as a component and a noxious and malodorous gas,comprising:a powdery adsorbent; a means for mixing the powdery adsorbentwith an exhaust gas so as to adhere particles of the exhaust gas to thepowdery adsorbent and so as to have the powdery adsorbent adsorb anoxious and malodorous gas component of the exhaust gas and forseparating powdery adsorbent having the particles adhered thereto andthe noxious and malodorous gas adsorbed thereby from the exhaust gasafter the exhaust gas has been at least partially purified, said meansfor mixing and separating comprising at least three dust separatorsconnected in series with each other, wherein each of said dustseparators has an inlet and a powdery adsorbent outlet, and wherein eachpowdery adsorbent outlet of said dust separators, except for the firstof said dust separators in series, is connected to the inlet of apreceding one of said dust separators in series; a means connected tosaid powdery adsorbent outlet of the first of said dust separators forregenerating the powdery adsorbent therefrom by heating the powderyadsorbent so as to remove the noxious and malodorous gas and theparticles therefrom so as to obtain a regenerated powdery adsorbent; anda means for conveying the regenerated powdery adsorbent from said meansfor regenerating to the inlet of the last of said dust separators inseries.
 12. An apparatus for treating an exhaust gas containingparticles that comprise organic compounds as a component and a noxiousand malodorous gas, comprising:an adsorbent; an exhaust gas line; anadsorbent feeding arrangement connected to said exhaust gas line forfeeding the adsorbent into said exhaust gas line; an adsorbent separatorconnected to said exhaust gas line by an exhaust gas inlet thereofdownstream of said adsorbent feeding arrangement, said adsorbentseparator further comprising an exhaust gas outlet and an adsorbentoutlet; an adsorbent regenerator connected to said adsorbent outlet ofsaid adsorbent separator, said adsorbent regenerator comprising a firstheat treating section connected to said adsorbent outlet and a secondheat treating section connected to said first heat treating section andhaving a regenerated adsorbent outlet; and an adsorbent conveyorconnecting said regenerated adsorbent outlet and said adsorbent feedingarrangement for conveying regenerated adsorbent to said feedingarrangement.
 13. The apparatus of claim 12, wherein said regeneratorfurther comprises a heated gas supply connected to said first heatingsection and said second heating section for supplying heated gasthereto.
 14. The apparatus of claim 12, wherein said adsorbent separatorcomprises a cyclone connected to said exhaust gas line and defining saidexhaust gas inlet, said cyclone having a gas outlet and a cycloneadsorbent outlet, and a bag filter defining having a gas outlet saidexhaust gas outlet, said bag filter having a bag filter inlet connectedto said gas outlet of said cyclone and a bag filter adsorbent outlet,said cyclone adsorbent outlet and said bag filter adsorbent outlet beingconnected to said adsorbent outlet of said adsorbent separator.
 15. Theapparatus of claim 14, wherein said adsorbent feeding arrangementcomprises a first adsorbent feeding nozzle in said exhaust gas line anda second adsorbent feeding nozzle in said gas outlet of said cyclone.16. The apparatus of claim 15, wherein said first and second adsorbentfeeding nozzles are connected to said adsorbent outlet of said adsorbentseparator and said adsorbent conveyor, respectively.
 17. The apparatusof claim 12, wherein each of said first and second sections of saidadsorbent regenerator comprises a heated air pneumatic conveyorconnected to a cyclone and a bag filter.
 18. The apparatus of claim 12,wherein said adsorbent regenerator has at least one gas outlet and theapparatus further comprises at least one of an adsorptive solventcollecting device and an oxidative cracker connected to said at leastone gas outlet of said adsorbent regenerator.
 19. A method of treatingan exhaust gas containing particles that comprise organic compounds as acomponent and a noxious and malodorous gas, said method comprising thesteps of:mixing a powdery adsorbent with an exhaust gas containingparticles that comprise organic compounds as a component and a noxiousand malodorous gas at a first location so as to adhere the particles ofthe exhaust gas to the powdery adsorbent and so as to have the powderyadsorbent adsorb the noxious and malodorous gas component of the exhaustgas; separating the powdery adsorbent having the particles adheredthereto and the noxious and malodorous gas adsorbed thereby from theexhaust gas after the exhaust gas has been at least partially purified;regenerating the powdery adsorbent that has been separated from theexhaust gas by first heating the powdery adsorbent at a firsttemperature sufficient to have the noxious and malodorous gas desorbedfrom the powdery adsorbent and then heating the powdery adsorbent at asecond temperature sufficient to thermally decompose the particles, thesecond temperature being higher than the first temperature, such thatregenerated powdery adsorbent results at a second location; andconveying the regenerated powdery adsorbent from the second location tothe first location for use in said step of mixing.
 20. The method ofclaim of 19, wherein the first temperature is 120° to 250° C. and thesecond temperature is 350° to 600° C.
 21. The method of claim 19,wherein in said step of regenerating both the first heating and thesecond heating are carried out by mixing the powdery adsorbent with aheated gas for regeneration of the powdery adsorbent.
 22. The method ofclaim 19, wherein the powdery adsorbent is a hydrophobic zeolite powder.23. The method of claim 19, wherein said step of mixing furthercomprises electrostatically charging the powdery adsorbent.
 24. Themethod of claim 19, and further comprising the step of detoxifying anddeodorizing the noxious and malodorous gas desorbed in said step ofregenerating.